The present invention relates to firefighter garments and, more particularly, to firefighter garments having discrete, multiple layers of material.
The National Fire Protection Association (NFPA) requires that firefighter garments must meet certain specific standards. As a minimum requirement, the garment must include an outer shell made of a flame-resistant material which preferably resists punctures and abrasion as well, an intermediate moisture barrier layer and an inner, thermal layer for protecting the wearer against external high-temperature extremes encountered during firefighting activities. Typically, the outer shell is made of a single layer of a tightly woven aramid material such as NOMEX III, KEVLAR ("NOMEX III" and "KEVLAR" are registered trademarks of E.I. DuPont de Nemours & Co., Inc.) or PBI ("PBI" is a registered trademark of Celanese Corp.).
The moisture barrier typically comprises a substrate of NOMEX, a blend of NOMEX and KEVLAR or a blend of polyester and cotton with a coating of flame retardant neoprene or GORE-TEX film ("GORE-TEX" is a registered trademark of W.L. Gore & Associates, Inc.). The thermal barrier layer typically comprises a light weight (3-3.5 ounce) facecloth of NOMEX quilted to a batting of aramid fibers or to layers of nonwoven, spunlaced material felt made up of NOMEX and KEVLAR fibers. The outer shell provides a flame-resistant covering for the garment, the moisture barrier prevents the wearer from becoming wet as a result of external moisture from fire hoses, sprinklers, and the like, and from steam burns and the inner thermal layer provides protection from external heat sources.
One problem inherent with many firefighter garments is that, while the three layers of material protect the wearer from external sources of flame, heat and moisture, they also act to retain the heat and perspiration moisture generated by the wearer. Such heat and moisture buildup can be considerable in the firefighting environment, in which the wearer is required to wear heavy clothing, carry people and heavy equipment, and climb stairs. As a result of such physical exertion, the core body temperature of the wearer of firefighter garments increases since thermal escape by radiation from the skin surface of the wearer and heat transport from evaporation of perspiration is reduced by the thermal layer. The latter problem is a result of the insulating effect of the thermal barrier layer, which tends to trap perspiration moisture and hold it close to the skin of the wearer. An increase of only a few degrees in body core temperature can significantly reduce the strength and endurance of a firefighter in the often hostile firefighting environment.
Attempts have been made to reduce the buildup of heat during strenuous firefighter activities. For example, Grilliot et al. U.S. Pat. No. 4,897,886 discloses a firefighter garment having an outer shell, a moisture barrier layer and an inner thermal layer. The inner thermal layer and moisture barrier are separated by a spacer element to maintain a "dead air space" between those layers of the garment. The dead air space prevents circulation of air between the inner and intermediate layers. In one embodiment, the spacer element comprises elongate channels which are oriented vertically on the garment so that heat entering the air space flows upwardly to exit the top of the garment through a porous inner layer.
Accordingly, there is a need for a firefighter garment which is lightweight, allows for escape of heat and perspiration vapor from the wearer, yet provides the requisite protection from external sources of flame, heat and moisture.